Advanced Materials Research Vol. 502

Abstract: By using the two-dimensional quasicontinuum method, the nanocontact between Ni indenter and single crystal Cu substrate with a smooth or rough surface is simulated. The contact force varies in a nonlinear fashion with the increasing indenter displacement, including several force drops. The atomic-scale deformation mechanism in the Cu substrate during nanocontact process is monitored. Shockley partials, Lomer-Cottrel locks as well as twinning faults are observed at the force drops. The Lomer-Cottrel locks play an important role in smooth surface nanocontact process, and they insure that Cu substrate undergoes elastic deformation dominantly during nanocontact process. The contact forces calculated from the Maugis-Dugale (M-D) theory show a good agreement with those obtained by the QC simulation in the smooth surface nanocontact process. It must be noted that the M-D theory is no longer suitable to describe the rough surface nanocontact problem due to the severe plastic deformation in the asperities of the substrate when the characteristic size of roughness is on the order of the indenter depth.

Abstract: The elastohydrodynamic lubrication (EHL) geometric model of the water lubricated rubber bearings under standard experimental conditions with water lubrication was established. The complete numerical solution of the EHL model was obtained by using multi-grid technique. The results show that the EHL state can be only established under high relative velocity and mild load conditions between the rubber block and the chromium coating on steel with sufficient water. The numerical results are good agreement with the experimental data.

Abstract: Angular type grippers are proper to grip the small size material than linear type grippers (clamping). It is due to the grip force of angular type grippers separates to the normal and the opposite directional force to gravity forces, when the contact between the gripper tip and the gripped material occurs. Whereas, the linear type gripper with prismatic joint has only normal forces. Therefore, even less gripping force of angular type grippers than linear type can generate slip-less pick-and-place motions. But this angular type gripper has some restrictions. For generating the opposite direction force to gravity forces, it is necessary that the length between each angular joint position is larger than the length of gripped materials. This should be considered on the design step of angular type grippers. Otherwise, the gripping force separates to the normal and the same directional force to gravity forces. The other restriction is that the tip of gripper must have passive joint or active joint for the plane-to-plane contact between faces of gripped material and gripper tip, for getting the high frictional coefficient. In this paper, we describe the case of adaptation of passive joint. This leads simpler implementation than the active joint. Especially, we focus on the torsional spring deposed at between jaw link and tip as the passive joint, with effects of design parameters of this torsional spring such as the torsional stiffness and preload with multi-body dynamics simulation.

Abstract: According to the geostress and casing structure data of Puguang gas field，mechanics and deformation law of nonstandard casing is studied on condition of non uniformity and high geostress. The results show that collapse strength has increased 51.75 MPa（270%）as thickness raise from 8.98 mm to 15.11 mm under uniform external loads. Under the nonuniform external loads, the collapse strength of casing has reduced 60% in some degree such as thickness is 13.84 mm. Application in site proves that nonstandard casing is feasible, which is significant for safe and efficient exploit in Puguang gas field.

Abstract: A improved algorithm to optimize the restraining force of equivalent drawbead was proposed base on BGFS(Broyden-Fletcher-Goldfarb-Shanno) algorithm combined with a simplified finite element method called inverse approach(IA). The forming limit curve (FLC) and the wrinkle limit curve (WLC) were considered as the objective function to reflect the influence of Fracture and wrinkle defect in sheet metal forming process. The optimized result was more accurate than those procedures only consider the variation of thickness distribution. The optimized process was also very efficient due to the simplified assumptions of the IA. Two stamping parts were presented to validate the accuracy of this optimum algorithm.

Abstract: There are two kinds of thinking strategy, which are vertical thinking and lateral thinking [1]. Nowadays, there are few computer-aided designs using design thinking strategy. Most computer aided designs combine the consumer's emotional and pattern matching. Base on this reason, this study's purpose is the application of design thinking strategy to computer-aided design, and use the Model of Two Paths which proposed by Tseng & Chang [2], and combined parametric modeling of derivatives design. The authors hope in the future, the computer systems can assist the designer in thinking. Currently, the study found the process of parametric modeling form generation that changes the spatial relation which is similar to Jumping thinking of lateral thinking. The shape evolution between different vocabulary is similar to Triggering thinking of lateral thinking [2].

Abstract: The dynamic finite element method is widely used in vibration structural analysis of engineering, and especially advantageous in high frequency vibration analysis comparing with traditional finite element method. It is the same with the electromagnetic waveguide problem. This paper studies the cut-off frequency and the propagation constant problem of waveguide by using the dynamic finite element format which is deduced through dual variational principle and the W-W algorithm. Compared with the common dual edge element method, this one can work out the propagation constant, cut-off frequency and modal more accurately, as well as with small degree of freedom.

Abstract: This paper introduces the physical model and the mathematical model for the submarine oil pipeline during shutdown time, and establish the heat transfer model for the shutdown time of submarine oil pipeline by using the software COMSOL Multiphysics. The permissive shutdown time for pipes of different diameters is calculated in specific case and the diameter-permissive shutdown time curve for the working condition is obtained, thus, provides theoretical support for rush repair which is required when pipe is forced to stop transmission as well as engineering design and safe operations. At the same time, this paper provides reference for the relationship between other factors and permissive shutdown time.

Abstract: this paper, focusing on the actuality and the features of the cold ring rolling, studies the forming principle of the rolling of multi-mandrel roller. Through the kinematics analysis of the rolling of ring multi-mandrel roller, the deformation simulation and the mechanical analysis of the infinitesimal gridding strain, this paper builds the infinitesimal deformation model of ring blank’s cold rolling, analyzes the deformation rules of the ring blank’s thickness direction rolled by the multi-mandrel roller and the relation between the tangential strain and the radial strain which should be satisfied by the mandrel roller’s movement values, and deduces out the mathematical expressions of the needed technological parameters like the minimum instantaneous rolling reduction. The research result can be used as the theoretical foundations for designing the multi-mandrel rolling miss and working out the rolling technology of the ring multi-mandrel roller.

Abstract: This paper discussed on the research of fatigue strength test of 20CrMnMo carburized and quenched gears. This test is done through a fatigue machine of high-frequency electromagnetic resonant with pulse double-tooth loading. In the short-life area, give four levels of constant stress group test; in the long-life area, adopt up-down test method. According to the experimental data obtained in the tests and statistical theory, complete the C-R-S-N curve, and assess the values of limit stress under different reliabilities.