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61-602: The Pioneer Mother Memorial , also known as Pioneer Mother and Pioneer Mothers , is a 1928 bronze sculpture by American artist Avard Fairbanks , installed at Esther Short Park in Vancouver, Washington , in the United States. The memorial depicts a mother and three children, and commemorates pioneer mothers who settled in the Pacific Northwest . The main female figure may depict Esther Short, one of

122-479: A patina , a process that allows some control over the colour and finish. Another form of sculptural art that uses bronze is ormolu , a finely cast soft bronze that is gilded (coated with gold) to produce a matte gold finish. Ormolu was popularized in the 18th century in France and is found in such forms as wall sconces (wall-mounted candle holders), inkstands, clocks and garnitures . Ormolu wares can be identified by

183-539: A (nominal) stress-strain curve, because the peak (representing the onset of necking) is often relatively flat. Moreover, some (brittle) materials fracture before the onset of necking, such that there is no peak. In practice, for many purposes it is preferable to carry out a different kind of test, designed to evaluate the toughness (energy absorbed during fracture), rather than use ductility values obtained in tensile tests. In an absolute sense, "ductility" values are therefore virtually meaningless. The actual (true) strain in

244-418: A clear ring when tapped, showing that they are made of bronze, not a cheaper alloy such as spelter or pewter . ductility Ductility refers to the ability of a material to sustain significant plastic deformation before fracture. Plastic deformation is the permanent distortion of a material under applied stress, as opposed to elastic deformation, which is reversible upon removing the stress. Ductility

305-405: A concrete and granite base that measures approximately 102 inches (2.6 m) × 18 feet (5.5 m) × 15 feet (4.6 m). Behind the figure group is a concrete backdrop. Its reverse side includes a bronze medallion with a bas- relief depicting a team of oxen pulling a covered wagon . The animals are led by a man, and an "anxious" woman and baby are in the wagon. A large barrel is attached to

366-412: A genuinely meaningful parameter. One objection is that it is not easy to measure accurately, particularly with samples that are not circular in section. Rather more fundamentally, it is affected by both the uniform plastic deformation that took place before necking and by the development of the neck. Furthermore, it is sensitive to exactly what happens in the latter stages of necking, when the true strain

427-511: A high ferrite content. This famously resulted in serious hull cracking in Liberty ships in colder waters during World War II , causing many sinkings. DBTT can also be influenced by external factors such as neutron radiation , which leads to an increase in internal lattice defects and a corresponding decrease in ductility and increase in DBTT. The most accurate method of measuring the DBTT of

488-557: A long dress, shawl, and shoes. She stands, facing forward, and holds a flintlock rifle in her proper right hand. The woman's opposite hand rests on the head of the taller of two girls at her proper left side. The taller girl holds the shorter one with her proper left hand, while the shorter girl faces the taller one and rests against the mother's proper left knee. A young boy clings to the mother's dress and leans against her rifle. The sculpture measures approximately 7 feet (2.1 m) × 3 feet (0.91 m) × 21 inches (53 cm) and rests on

549-557: A material is by fracture testing . Typically four-point bend testing at a range of temperatures is performed on pre-cracked bars of polished material. Two fracture tests are typically utilized to determine the DBTT of specific metals: the Charpy V-Notch test and the Izod test. The Charpy V-notch test determines the impact energy absorption ability or toughness of the specimen by measuring the potential energy difference resulting from

610-521: A material is cooled below the DBTT, it has a much greater tendency to shatter on impact instead of bending or deforming ( low temperature embrittlement ). Thus, the DBTT indicates the temperature at which, as temperature decreases, a material's ability to deform in a ductile manner decreases and so the rate of crack propagation drastically increases. In other words, solids are very brittle at very low temperatures, and their toughness becomes much higher at elevated temperatures. For more general applications, it

671-406: A number of mechanical applications. Historical bronzes are highly variable in composition, as most metalworkers probably used whatever scrap was on hand; the metal of the 12th-century English Gloucester Candlestick is bronze containing a mixture of copper, zinc, tin, lead, nickel, iron, antimony, arsenic with an unusually large amount of silver – between 22.5% in the base and 5.76% in

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732-431: A plaster is a means of preserving the artwork until a patron may be found to finance a bronze casting, either from the original moulds or from a new mould made from the refined plaster positive. Once a production mould is obtained, a wax (hollow for larger sculptures) is then cast from the mould. For a hollow sculpture, a core is then cast into the void, and is retained in its proper location (after wax melting) by pins of

793-796: A similar mechanical property, is characterized by a material's ability to deform plastically without failure under compressive stress. Historically, materials were considered malleable if they were amenable to forming by hammering or rolling. Lead is an example of a material which is relatively malleable but not ductile. Ductility is especially important in metalworking , as materials that crack, break or shatter under stress cannot be manipulated using metal-forming processes such as hammering , rolling , drawing or extruding . Malleable materials can be formed cold using stamping or pressing , whereas brittle materials may be cast or thermoformed . High degrees of ductility occur due to metallic bonds , which are found predominantly in metals; this leads to

854-1205: A tension test are relative elongation (in percent, sometimes denoted as ε f {\displaystyle \varepsilon _{f}} ) and reduction of area (sometimes denoted as q {\displaystyle q} ) at fracture. Fracture strain is the engineering strain at which a test specimen fractures during a uniaxial tensile test . Percent elongation, or engineering strain at fracture, can be written as: % E L = final gauge length - initial gauge length initial gauge length = l f − l 0 l 0 ⋅ 100 {\displaystyle \%EL={\frac {\text{final gauge length - initial gauge length}}{\text{initial gauge length}}}={\frac {l_{f}-l_{0}}{l_{0}}}\cdot 100} Percent reduction in area can be written as: % R A = change in area original area = A 0 − A f A 0 ⋅ 100 {\displaystyle \%RA={\frac {\text{change in area}}{\text{original area}}}={\frac {A_{0}-A_{f}}{A_{0}}}\cdot 100} where

915-578: Is a critical mechanical performance indicator, particularly in applications that require materials to bend, stretch, or deform in other ways without breaking. The extent of ductility can be quantitatively assessed using the percent elongation at break, given by the equation: % E L = ( l f − l 0 l 0 ) × 100 {\displaystyle \%EL=\left({\frac {l_{f}-l_{0}}{l_{0}}}\right)\times 100} where l f {\displaystyle l_{f}}

976-555: Is also applied to metal sculptures made by electrotyping (or galvanoplasty), although these sculptures are typically pure copper and their fabrication does not involve metal casting. In lost-wax or investment casting, the artist starts with a full-sized model of the sculpture, most often a non-drying oil-based clay such as Plasticine model for smaller sculptures or for sculptures to be developed over an extended period (water-based clays must be protected from drying), and water-based clay for larger sculptures or for sculptures for which it

1037-681: Is applied to the material. Thus, in materials with a lower amount of slip systems, dislocations are often pinned by obstacles leading to strain hardening, which increases the materials strength which makes the material more brittle. For this reason, FCC (face centered cubic) structures are ductile over a wide range of temperatures, BCC (body centered cubic) structures are ductile only at high temperatures, and HCP (hexagonal closest packed) structures are often brittle over wide ranges of temperatures. This leads to each of these structures having different performances as they approach failure (fatigue, overload, and stress cracking) under various temperatures, and shows

1098-406: Is desired to capture a gestural quality – one that transmits the motion of the sculptor in addition to that of the subject. A mould is made from the clay pattern, either as a piece mould from plaster, or using flexible gel or similar rubber-like materials stabilized by a plaster jacket of several pieces. Often a plaster master will be made from this mould for further refinement. Such

1159-525: Is installed at Esther Short Park's north entrance, at the intersection of West 8th and Daniel Street (between Columbia and Esther Streets) in Vancouver, Washington. The park commemorates the pioneer woman and her husband Amos, who were among the first U.S. citizens to arrive in Fort Vancouver . Some sources say the memorial sculpture commemorates Esther Short specifically, while also "[typifying] all

1220-410: Is no dependence for properties such as stiffness, yield stress and ultimate tensile strength). This occurs because the measured strain (displacement) at fracture commonly incorporates contributions from both the uniform deformation occurring up to the onset of necking and the subsequent deformation of the neck (during which there is little or no deformation in the rest of the sample). The significance of

1281-591: Is often becoming very high and the behavior is of limited significance in terms of a meaningful definition of strength (or toughness). There has again been extensive study of this issue. Metals can undergo two different types of fractures: brittle fracture or ductile fracture. Failure propagation occurs faster in brittle materials due to the ability for ductile materials to undergo plastic deformation. Thus, ductile materials are able to sustain more stress due to their ability to absorb more energy prior to failure than brittle materials are. The plastic deformation results in

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1342-404: Is preferred to have a lower DBTT to ensure the material has a wider ductility range. This ensures that sudden cracks are inhibited so that failures in the metal body are prevented. It has been determined that the more slip systems a material has, the wider the range of temperatures ductile behavior is exhibited at. This is due to the slip systems allowing for more motion of dislocations when a stress

1403-407: Is removed to reduce the likelihood of interior corrosion. Incomplete voids created by gas pockets or investment inclusions are then corrected by welding and carving. Small defects where sprues and vents were attached are filed or ground down and polished. For a large sculpture, the artist will usually prepare small study models until the pose and proportions are determined. An intermediate-sized model

1464-641: Is the length of the material after fracture and l 0 {\displaystyle l_{0}} is the original length before testing. This formula helps in quantifying how much a material can stretch under tensile stress before failure, providing key insights into its ductile behavior. Ductility is an important consideration in engineering and manufacturing. It defines a material's suitability for certain manufacturing operations (such as cold working ) and its capacity to absorb mechanical overload like in an engine. Some metals that are generally described as ductile include gold and copper , while platinum

1525-492: Is the most ductile of all metals in pure form. However, not all metals experience ductile failure as some can be characterized with brittle failure like cast iron . Polymers generally can be viewed as ductile materials as they typically allow for plastic deformation. Inorganic materials, including a wide variety of ceramics and semiconductors, are generally characterized by their brittleness. This brittleness primarily stems from their strong ionic or covalent bonds, which maintain

1586-405: Is then constructed with all of the final details. For very large works, this may again be scaled to a larger intermediate. From the final scale model, measuring devices are used to determine the dimensions of an armature for the structural support of a full-size temporary piece, which is brought to rough form by wood, cardboard, plastic foam, and/or paper to approximately fill the volume while keeping

1647-618: The Indus Valley Civilisation and dating back to c.  2500 BCE , is perhaps the first known bronze statue. Life-sized bronze statues in Ancient Greece have been found in good condition; one is the seawater-preserved bronze Victorious Youth that required painstaking efforts to bring it to its present state for museum display. Far more Roman bronze statues have survived. The ancient Chinese knew both lost-wax casting and section mould casting, and during

1708-527: The Shang dynasty created large numbers of Chinese ritual bronzes , ritual vessels covered with complex decoration, which were buried in sets of up to 200 pieces in the tombs of royalty and the nobility. Over the long creative period of Egyptian dynastic art, small lost-wax bronze figurines were made in large numbers; several thousand of them have been conserved in museum collections. The 7th-8th century Sri Lankan Sinhalese bronze statue of Buddhist Tara , now in

1769-679: The British Museum, is an excellent example of Sri Lankan bronze statues. From the ninth through the thirteenth century the Chola dynasty in South India represented the pinnacle of bronze casting in India. Making bronzes is highly skilled work, and a number of distinct casting processes may be employed, including lost-wax casting (and its modern-day spin-off investment casting ), sand casting and centrifugal casting . The term "bronze"

1830-454: The Charpy test, with the only differentiating factor being the placement of the sample; In the former the sample is placed vertically, while in the latter the sample is placed horizontally with respect to the bottom of the base. For experiments conducted at higher temperatures, dislocation activity increases. At a certain temperature, dislocations shield the crack tip to such an extent that

1891-615: The City of Vancouver's Parks & Recreation department. Bronze sculpture Common bronze alloys have the unusual and desirable property of expanding slightly just before they set, thus filling the finest details of a mould. Then, as the bronze cools, it shrinks a little, making it easier to separate from the mould. Their strength and ductility (lack of brittleness) is an advantage when figures in action poses are to be created, especially when compared to various ceramic or stone materials (such as marble sculpture ). These qualities allow

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1952-441: The area of concern is the cross-sectional area of the gauge of the specimen. According to Shigley's Mechanical Engineering Design, significant denotes about 5.0 percent elongation. An important point concerning the value of the ductility (nominal strain at failure) in a tensile test is that it commonly exhibits a dependence on sample dimensions. However, a universal parameter should exhibit no such dependence (and, indeed, there

2013-690: The atoms in a rigid, densely packed arrangement. Such a rigid lattice structure restricts the movement of atoms or dislocations, essential for plastic deformation. The significant difference in ductility observed between metals and inorganic semiconductor or insulator can be traced back to each material’s inherent characteristics, including the nature of their defects, such as dislocations, and their specific chemical bonding properties. Consequently, unlike ductile metals and some organic materials with ductility (% EL) from 1.2% to over 1200%, brittle inorganic semiconductors and ceramic insulators typically show much smaller ductility at room temperature. Malleability ,

2074-490: The brave mothers of the frontier" who settled in the Pacific Northwest . Some sources say the sculpture's main female figure is Short herself, per the dedication ceremony's program. The sculpture was cast in Florence, Italy , where Fairbanks was working on his Guggenheim Fellowship . The memorial features a full-length bronze figure depicting a mother and three children. The woman wears traditional pioneer clothing, including

2135-531: The ceremony. The artist was commissioned to create the memorial by Vancouver banker Edward Crawford and his wife Ida, who donated $ 10,000 to its creation. The work was classified as needing treatment by the Smithsonian Institution 's " Save Outdoor Sculpture! " program in May 1995. It was renovated as part of park improvement efforts around the start of the 21st century. The memorial is maintained by

2196-409: The collision between a mass on a free-falling pendulum and the machined V-shaped notch in the sample, resulting in the pendulum breaking through the sample. The DBTT is determined by repeating this test over a variety of temperatures and noting when the resulting fracture changes to a brittle behavior which occurs when the absorbed energy is dramatically decreased. The Izod test is essentially the same as

2257-405: The common perception that metals are ductile in general. In metallic bonds valence shell electrons are delocalized and shared between many atoms. The delocalized electrons allow metal atoms to slide past one another without being subjected to strong repulsive forces that would cause other materials to shatter. The ductility of steel varies depending on the alloying constituents. Increasing

2318-516: The concrete backdrop below the medallion is the signed inscription: ERECTED IN MEMORY OF / THE PIONEER MOTHERS / THROUGH THE GIFT OF / MR. & MRS. E. G. CRAWFORD / 1928 . The Pioneer Mother Memorial is one of Vancouver's oldest works of public art (the oldest, according to the Clark County Historical Museum ), acquired in 1928 and unveiled on July 21, 1929 (or September 7, according to some sources). Fairbanks attended

2379-424: The contribution from neck development depends on the "aspect ratio" (length / diameter) of the gauge length, being greater when the ratio is low. This is a simple geometric effect, which has been clearly identified. There have been both experimental studies and theoretical explorations of the effect, mostly based on Finite Element Method (FEM) modelling. Nevertheless, it is not universally appreciated and, since

2440-546: The creation of extended figures, as in Jeté , or figures that have small cross sections in their support, such as the equestrian statue of Richard the Lionheart . But the value of the bronze for uses other than making statues is disadvantageous to the preservation of sculptures; few large ancient bronzes have survived, as many were melted down to make weapons or ammunition in times of war or to create new sculptures commemorating

2501-426: The dislocations require a larger stress to cross the grain boundaries and continue to propagate throughout the material. It has been shown that by continuing to refine ferrite grains to reduce their size, from 40 microns down to 1.3 microns, that it is possible to eliminate the DBTT entirely so that a brittle fracture never occurs in ferritic steel (as the DBTT required would be below absolute zero). In some materials,

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2562-400: The first U.S. citizens to arrive in Fort Vancouver . Commissioned by Vancouver banker Edward Crawford and his wife Ida for $ 10,000, it is one of the city's oldest works of public art, acquired in 1928 and unveiled in 1929. The sculpture was renovated around the start of the 21st century and is maintained by the City of Vancouver's Parks & Recreation department. The Pioneer Mother Memorial

2623-473: The fractured ends), divided by the original sectional area. It is sometimes stated that this is a more reliable indicator of the "ductility" than the elongation at failure (partly in recognition of the fact that the latter is dependent on the aspect ratio of the gauge length, although this dependence is far from being universally appreciated). There is something in this argument, but the RA is still some way from being

2684-414: The importance of the DBTT in selecting the correct material for a specific application. For example, zamak 3 exhibits good ductility at room temperature but shatters when impacted at sub-zero temperatures. DBTT is a very important consideration in selecting materials that are subjected to mechanical stresses. A similar phenomenon, the glass transition temperature , occurs with glasses and polymers, although

2745-409: The levels of carbon decreases ductility. Many plastics and amorphous solids , such as Play-Doh , are also malleable. The most ductile metal is platinum and the most malleable metal is gold . When highly stretched, such metals distort via formation, reorientation and migration of dislocations and crystal twins without noticeable hardening. The quantities commonly used to define ductility in

2806-460: The material following a modification of the Griffith equation, where the critical fracture stress increases due to the plastic work required to extend the crack adding to the work necessary to form the crack - work corresponding to the increase in surface energy that results from the formation of an addition crack surface. The plastic deformation of ductile metals is important as it can be a sign of

2867-410: The mechanism is different in these amorphous materials . The DBTT is also dependent on the size of the grains within the metal, as typically smaller grain size leads to an increase in tensile strength, resulting in an increase in ductility and decrease in the DBTT. This increase in tensile strength is due to the smaller grain sizes resulting in grain boundary hardening occurring within the material, where

2928-402: The metal transitions from a brittle behavior to a ductile behavior, or from a ductile behavior to a brittle behavior, is known as the ductile-brittle transition temperature (DBTT). Below the DBTT, the material will not be able to plastically deform, and the crack propagation rate increases rapidly leading to the material undergoing brittle failure rapidly. Furthermore, DBTT is important since, once

2989-451: The model is made in wax, possibly formed over a core, or with a core cast in place, if the piece is to be hollow. If no mould is made and the casting process fails, the artwork will also be lost. After the metal has cooled, the external ceramic or clay is chipped away, revealing an image of the wax form, including core pins, sprues, vents, and risers. All of these are removed with a saw and tool marks are polished away, and interior core material

3050-412: The neck at the point of fracture bears no direct relation to the raw number obtained from the nominal stress-strain curve; the true strain in the neck is often considerably higher. Also, the true stress at the point of fracture is usually higher than the apparent value according to the plot. The load often drops while the neck develops, but the sectional area in the neck is also dropping (more sharply), so

3111-611: The pan below the candle. The proportions of this mixture may suggest that the candlestick was made from a hoard of old coins. The Benin Bronzes are really brass , and the Romanesque Baptismal font at St Bartholomew's Church, Liège is described as both bronze and brass. In the Bronze Age, two forms of bronze were commonly used: "classic bronze", about 10% tin, was used in casting; and "mild bronze", about 6% tin,

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3172-428: The potential failure of the metal. Yet, the point at which the material exhibits a ductile behavior versus a brittle behavior is not only dependent on the material itself but also on the temperature at which the stress is being applied to the material. The temperature where the material changes from brittle to ductile or vice versa is crucial for the design of load-bearing metallic products. The minimum temperature at which

3233-414: The range of sample dimensions in common use is quite wide, it can lead to highly significant variations (by factors of up to 2 or 3) in ductility values obtained for the same material in different tests. A more meaningful representation of ductility would be obtained by identifying the strain at the onset of necking, which should be independent of sample dimensions. This point can be difficult to identify on

3294-481: The same metal used for casting. One or more wax sprues are added to conduct the molten metal into the sculptures - typically directing the liquid metal from a pouring cup to the bottom of the sculpture, which is then filled from the bottom up in order to avoid splashing and turbulence. Additional sprues may be directed upward at intermediate positions, and various vents may also be added where gases could be trapped. (Vents are not needed for ceramic shell casting, allowing

3355-481: The sprue to be simple and direct). The complete wax structure (and core, if previously added) is then invested in another kind of mould or shell, which is heated in a kiln until the wax runs out and all free moisture is removed. The investment is then soon filled with molten bronze. The removal of all wax and moisture prevents the liquid metal from being explosively ejected from the mould by steam and vapour. Students of bronze casting will usually work in direct wax, where

3416-407: The transition is sharper than others and typically requires a temperature-sensitive deformation mechanism. For example, in materials with a body-centered cubic (bcc) lattice the DBTT is readily apparent, as the motion of screw dislocations is very temperature sensitive because the rearrangement of the dislocation core prior to slip requires thermal activation. This can be problematic for steels with

3477-469: The true stress there is rising. There is no simple way of estimating this value, since it depends on the geometry of the neck. While the true strain at fracture is a genuine indicator of "ductility", it cannot readily be obtained from a conventional tensile test. The Reduction in Area (RA) is defined as the decrease in sectional area at the neck (usually obtained by measurement of the diameter at one or both of

3538-500: The victors, while far more stone and ceramic works have come through the centuries, even if only in fragments. As recently as 2007 several life sized bronze sculptures by John Waddell were stolen, probably due to the value of the metal after the work has been melted. There are many different bronze alloys. Typically modern bronze is 88% copper and 12% tin . Alpha bronze consists of the alpha solid solution of tin in copper. Alpha bronze alloys of 4–5% tin are used to make coins and

3599-417: The wagon. The bottom of the medallion includes a relief of a cattle skull. The medallion has a diameter of approximately 36 inches (91 cm). The memorial includes several inscriptions. One by the woman's foot reads, Avard Fairbanks / 1928 . The medallion has two inscriptions: one below the wagon displays a copyright symbol and reads, 1928 Avard Fairbanks , while another says, THE / PIONEER / MOTHERS . On

3660-497: The weight low. Finally, plaster, clay or other material is used to form the full-size model, from which a mould may be constructed. Alternatively, a large refractory core may be constructed, and the direct-wax method then applied for subsequent investment. Before modern welding techniques, large sculptures were generally cast in one piece with a single pour. Welding allows a large sculpture to be cast in pieces, then joined. After final polishing, corrosive materials may be applied to form

3721-429: Was hammered from ingots to make sheets. Bladed weapons were mostly cast from classic bronze, while helmets and armour were hammered from mild bronze. According to one definition, modern "statuary bronze" is 90% copper and 10% tin. The great civilizations of the old world worked in bronze for art, from the time of the introduction of the alloy for tools and edged weapons. Dancing Girl from Mohenjo-daro , belonging to

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