Proposal of Experimental Equation for Elastic Modulus of Polymers Influence of Hydrostatic Pressure，Environmental Temperature and Strain Rate

December 27，1995

Tetsuya AYA and Toshio NAKAYAMA

A scalar potential model based on intermolecular force is proposed which can be used to understand the influence of factor，such as hydrostatic pressure，environmental temperature and strain rate，on the elastic modulus and elastic behavior of polymers．Wepropose an experimental equation for the elastic moduls taking into account the influence of the above‐mentioned factors．The hydrostatic pressure is considered to influence the elastic behaviof in so far as it is related to volumetric deformation．The environmental temperature is considered to influence in relation to the thermal expansion．The influence of strain rate is considered in relation to the discrete process of the elastic deformation．The experimental equation pfoposed approximately describe the influence of these factors . It is concluded that this model is useful for understanding and analyzing the elastic moduli and the constitutive relations of the elastic deformation of polymefs．

Keywords:Tension test，Polymer，Elastic modulus，Young's modulus， Intemolecular force，Potential theory，Elastic deformation，Hydrostaic pfessure，Environmental temperature，Strain rate



Optimum Square Shape Forming for Heat Exchangers Using Uniform Moment Bending Method .
Dieless Forming Technique for Double Layered Heat Exchangers II

(Received on September 27, 1995)

Toshiyuki AMIMOTO, Takashi ISHIGAMI, Hiroya MURAKAMI, Mitsuru KURAGANO and Minoru SATOH

Recently, consumer demand for high-quality, Iow-cost, energy-efficient air conditioners has risen for use In shops and offices. Production rationalization of the principal air condltioner component, the heat exchanger, was reguired for realization of a competitive, Iight-weight and easy-to-assemble product. Therefore, a new dieless forming technlque was proposed and a formlng machine using this new method, whlch is called the uniform moment bending method (UMB method), was developed to form square-shaped double-layered heat exchangers. Thls new method is conducted by means of four-axls numerical control technique instead of the conventional bending dies in order to form workpieces wlth uniform bending moment. By assuming that the neutral plane exlsts 5.25mm Inward from the center axls of the inner layer pipe of the heat exchanger, forming was accomplished with arc-shape error of 0.38ｱ0.44mm. Not only the arc shape, but other characteristics such as pipe flatness, formed angles, fin damage and productlon speed have satisfactorily met product specifications.

Keywords:die bending, dieless bending, bending moment, plastic theory, bending machine



Comparison of One-Side Compressing System and Both-Sides Compressing One Precision Cold Die Forging of Actual Gear Toothed Products Utilizing Divided Flows II

(Received on November 2, 1995)

Kyoichi OMEGA, Fumio MURAKOSHI, Hiroyuki ANDO, Kouji MIYOSHI and Kazuyoshi KONDO

In order to decrease the working pressure required for complete material filling of a die cavity, the divided flow method based on a both-sides compressing system is newly adopted. In this system, both an upper punch and a lower one move simultaneously. When the both-sides compressing system is used, the following results are obtained. (1) The pressure required for complete material filling is more than 500MPa lower than that required for using a one-side compressing system where only an upper punch moves. (2) For a low carbon steel such as S1OC, a well-shaped involute spur gear can be forged under a working pressure of about 1500MPa when the tooth width of the product is about 4.5 times the module. (3) When the compressive stress reaches about 1950MPa in a chromium alloyed steel or about 2300MPa in a Ni-Cr-Ho steel, a gear with the same results as those mentioned above for SIOC can be obtained without any intermediate annealing or relubrication treatment. (4) All the working pressures in the above-mentioned three cases are approximate-ly equal to 2.3 times the material flow resistance. Therefore, the divided flow method based on the both-sides compressing system is confirmed to be much more effective than that based on the one-side compressing one to decrease the pressure required for complete material filling of a die cavity.

Keywords:precise cold die forging, divided flow method, both-sides compressing system, steel material, spur gear, liquid lubricant, low working pressure.



Metal Flow Characteristics and Deformation Analyses in Hot Extrusion of 6063，5052 and 5083 Al‐Alloys

（Received on November 8，1995）

Hiroyuki KINOSHITA，Kenji NAKANISHI，Shunpei KAMITANI and Takuya YOSHIDA

Deしailed analyses ofしhe metal flow characteristics of Al-Mg Si alloy（6063）and Al-Mg al1oys（5052 and 5083）were carried out in a series of plane strain hot extrusion experiments．Symmetric flat dies with a 90deg.die angle and nonsymmetric wedge dies with 90deg.and l5deg.die angles were employed to investigate dead meしal zone formation and friction conditions in the hot extrusion process．Distributions of flowvelocity，effective strain rate and effective strain in the deformation zone insteady state extrusion were also analyzed quantitatively‐Flow curves and extrusion curves of 5052 and 5083 alloys have a higher load level thanしhose of 6063 alloy.The shearing plane along the dead metal zone is steeper in extrusion of 5052 and 5083 alloys than in that of 6063 alloy.A dead metal zone is formed in 5052 and 5083 alloys on both the 90 and l5 deg.die angle sides，while a dead metal zone is formed in 6063 alloy on only the 90 deg.die angle side．The fIow curves of 5083 alloy show work‐softening due to dynamic recrystallization at the hot extrusion temperature．Therefore，the velocity distribution pattern of 5083 alloy is diffe-rent from those of 6063 and 5052 alloys．

Keywords:Hot extrusion，aluminum alloy，dead metal zone，flow curve．



Dimensional Accuracy of Rectangular Extruded Pipes by 4 Portholes Die Study on Improvement in Quality of Hollow Extrusions　｡

(Received on December 25, 1995)

Satoshi MURAKAMI, Norio TAKATSUJI, Mitsugu TOKIZAWA, Kenji MATSUKI, Mitsuyuki ISOGAI and Seiichi NAGAO

The effect of the shape of 4 portholes on the welding strength and dimensional accuracy of rectangu]ar extruded pipes is investigated using the extrusion test The welding strength of rectangular extruded pipes obtained using the expanding test is unrelated to the shape of portholes and was determined to be approximately the same for ail 4 porthole shapes The circularity of rectangular extruded pipes is influenced much more by port Bc situated at the center of the die than by port Bo situated at the comer. The circularity and dimensional accuracy of rectangular extruded pipes worsen with increasing metal f]ow from port B and a high energy zone is formed at the bottom of the welding chamber near the thick wail die opning.

Keywords:extrusion, porthole die, extrusion pressure, welding strength, rectangular extruded pipes.shape of porthole, circularity, dimensional accuracy welding chamber.



Effect of Asymmetrical Cross Section on Out of Plane Deformation in Bending Processes of a Deformed Bar Bending Processes of a Deformed Bar for Reinforced Concrete I

(Received on December 25, 1995)

Masashi DAIMARUYA, Hidetoshi KOBAYASHI, Atsushi ITO, Tatsuro EBIHARA, Yutaka TODA and Wataru NOZAKI

It is required at present to improve the processing quality, especially the behavior of bending deformation of a deformed steel bar for reinforced concrete in the case of continuous bending treatment. When a deformed steel bar is bent in a vertical plane, the vertical displacement must be accompanied with a horizontal displacement deviating from the vertical plane. This phenomenon may be caused by the change of neutral axis position due to asymmetry of the section and the change of section shape along the bar. Elastoplastic bending tests of a cantilever composed of deformed steel bars are carried out to examine the behavior of the deformed bars in bending deformation. The direction of motion of the bar end is predicted based on an elastic bending theory for a bar with asymmetric cross section, although the deformations in the actual bending tests are beyond the elastic region. It is found that the direction of motion of the bar end observed in the elastoplastic bending experiments shows reasonable agreement with the prediction based on the elastic bending theory and that the out of plane bending deformation is mainly governed by the change of neutral axis position in the elastic region. Based on these results, an improved deformed-steel bar is designed and investigated.

Keywords:material testing, bending, reinforced concrete. deformed steel bar, asymmetric bending deformation. variable cross section, change of neutral axis



Measurement of Contact Pressure in Experiment with Plasticine

(Received on February 5, 1996)

Yukio KOJIMA, Toshiya KOHGA Toshihiro MIZUNO, and Takaji MIZUNO

A method for measuring the contact pressure distribution in a tool-workpiece interface is proposed, and the validity of the method is confirmed experimentally. An external groove is cut in the tool. The elastic deformation of the remaining diaphragmatic part is measured using strain gages, and is converted into the pressure. The interface condition is not disturbed by the measurement and a sophisticated sensor such as a pressure pin is not necessary. The method is applied to compression of Plasticine blocks and forward extrusion of a cylindrical Plasticine billet. The pressure distributions were similar to the measured strain distributions. The pressure distributions were estimated more accurately using the inverse analysis method which minimizes the difference between the calculated and measured strain distributions. The pressure distributions thus obtained were in agreement with those reported by other researchers.

Keywords: Material testing. measurement, strain measurement, contact pressure, inverse analysis, compression test,forward extrusion, experimental analysis, model simulation, Plasticine.



Elucidation of Wear Phenomena of Shearing Tools by Means of Visioplasticity

(Received on February 13, 1996)

Nobuhiro KOGA, Nobuki YUKAWA, Kou OIKAWA Masao MURAKAWA and Takashi JIMMA

In order to clarify the wear mechanism of shearing tools, wc used a two-halves sample material with grid patterns printed on a side surface and the surfaces contacting the tool during shearing of the sample, and calculated various stresses in the sample material using our automated visioplasticity system. Thus we derived the pressure distribution within the sample material which enabled us to calculate the normal stresses imposed on the shearing tool. At the same time, the intersection coordinate values measured from initial and deformed grid patterns were used to calculate the specific amount of material slip on the tool surfaces during shearing. For cantilever-type shearing, it was found that both the pressure and specific slip amount increase with decreasing distance from the punch and die edge in the cases of material constraint conditions wherein neither blank holder pressure nor counter pressure is applied, or both blank holder pressure and counted pressure are applied. However, when only blank holder pressure is applied without counter pressure, both pressure and specific slip amount exhibit maximum values a short distance away from the punch edge. These analytical speculations basically agree with the results of a FEM analysis and a shearing tool wear test performed in the same study.

Keywords:shearing, tool wear, visioplasticity, experimentai analysis, grid method, pressure distribution, slip amount, FEM