Two-stage magnetic-elasto-pulse stamping of thin sheet parts

The article substantiates the use of preliminary static loading and subsequent forging force when stamping thin sheet parts of complex shape with an elastic punch. The static load provides a relative deformation of the order of 20– 30% in the processing zone, which guarantees the stability of the position of the workpiece during subsequent pulsed loading. This technique is very important in the manufacture of asymmetric parts with a thickness of 0.01 – 0.3 mm. As a result, the accuracy of the products obtained corresponds to the 7th grade.The article provides a schematic diagram and a description of the proposed design of a double-action press, and analyzes the cyclogram of the device.It is recommended to carry out a static load with an electric drive, a pulsed one with a magnetic hammer, which is connected to a generator of impulse currents with a capacitive storage with an energy capacity of up to 40 kJ with a natural discharge frequency of the current of 20 kHz.

Forming containers for PCM materials using a hydrotechnical method with an elastomer

In this work, the authors present the method of forming by oil exerting pressure on the elastic punch forming the shape of a container for phase change material (PCM). Thanks to the use of two elastomer plates with a hardness of 65 and 80 Shore, the obtained part has mapped stiffeners in the middle and the appropriate depth of the bowl. This method is not widespread due to the precise design ensuring tightness of the load system of the formed blank. By reducing the tool costs, this method is used in particular in the case of unit production of prototype parts or small production series. The authors carried out tests of mechanical properties of the material, numerical analysis of feasibility with the FEM, real (workshop) trials after previous optimization by trial and error through structural changes of the tool. This allowed to obtain the best material drawing parameters for given boundary conditions. The research allowed to eliminate significant stresses and thinning in finished parts and corners of PCM containers.

Directional Thickness Alteration of a Thin-Walled Ring Blank Using Flanging and Forming for the Purpose of Receiving Conical Part

In this article the flanging method of thin-walled ring blanks using the elastic punch and rigid die scheme is investigated. Presence of a cylindrical portion near the larger edge and a flat area at the side of the blank hole is mandatory. Such conditions allow producing conical parts with minimal thickness variation by altering height of the cylindrical portion. Conducted experimental studies showed that the minimal thickness variation values are not exceeding 16% for different materials and relative thicknesses less than 0,01.

Adhesion and pull-off force of an elastic indenter from an elastic half-space

The adhesion between an elastic punch and an elastic half-space is investigated for plane and axisymmetric geometries. The pull-off force is determined for a range of material combinations. This configuration is characterized by a generalized stress intensity factor which has an order less than one-half. The critical value of this generalized stress intensity factor is related to the work of adhesion, under tensile loading, by using a cohesive zone model in an asymptotic analysis of the separation near the elastic punch corner. These results are used in conjunction with existing results in the literature for the frictionless contact between an elastic semi-infinite strip and half-space in both plane and axisymmetric configurations. It is found that the value of the pull-off force includes a dependence on the maximum stress of the cohesive zone model. As expected, this dependence vanishes as the punch becomes rigid in that case the order of the singularity approaches one-half. At the other limit, when the half-space becomes rigid, the stresses become bounded and uniform and the pull-off force depends linearly on the cohesive stress and is independent of the work of adhesion. Thus, the transition from fracture-dominated adhesion to strength-dominated adhesion is demonstrated.