A multi-diameter tubular body is cold-forged by forming a large-diameter hole portion in a formed body having a preliminary hole through subjection of the preliminary hole to deep hole forming and by punching out the bottom surface of the large-diameter hole portion to thereby form a small-diameter hole portion. Since a punch having a central protrusion on its forward end surface is used, an internal flaw is generated by dead metal in the inner circumferential surface of a depression, formed by the protrusion, in the bottom surface of the large-diameter hole portion. An outside diameter of a protrusion of a deep hole forming punch is rendered smaller than an inside diameter of the small-diameter hole portion to be formed later by punching out the bottom surface of the large-diameter hole portion. As a result, the internal flaw is removed when the small-diameter hole portion is formed.

A multi-diameter tubular body is cold-forged by forming a large-diameter hole portion in a formed body having a preliminary hole through subjection of the preliminary hole to deep hole forming and by punching out the bottom surface of the large-diameter hole portion to thereby form a small-diameter hole portion. Since a punch having a central protrusion on its forward end surface is used, an internal flaw is generated by dead metal in the inner circumferential surface of a depression, formed by the protrusion, in the bottom surface of the large-diameter hole portion. An outside diameter of a protrusion of a deep hole forming punch is rendered smaller than an inside diameter of the small-diameter hole portion to be formed later by punching out the bottom surface of the large-diameter hole portion. As a result, the internal flaw is removed when the small-diameter hole portion is formed.

A joining method is a method of joining a plate set composed by a plurality of stacked plate members including a first plate member and a second plate member by using a tapping screw. When the tapping screw is advanced into the plate set while the tapping screw is rotated in a state of applying a pressure onto the plate set so as to form through-holes in the first plate member and the second plate member, a first pressure applied onto the tapping screw is reduced down to a second pressure at the time when the tapping screw penetrates the first plate member.

A joining method is a method of joining a plate set composed by a plurality of stacked plate members including a first plate member and a second plate member by using a tapping screw. When the tapping screw is advanced into the plate set while the tapping screw is rotated in a state of applying a pressure onto the plate set so as to form through-holes in the first plate member and the second plate member, a first pressure applied onto the tapping screw is reduced down to a second pressure at the time when the tapping screw penetrates the first plate member.

Electrically assisted flow drill screwdriving processes (EAFDS) and devices are described. The methods can augment traditional FDS and allow for softening of metals of a stack-up, which can enable FDS joining of thicker and stronger materials such as boron steel. EAFDS methods can reduce cycle time and can be used to join thicker cross-sections with reduced installation torque. Also disclosed are fixtures for attachment to existing devices that can provide for the electrical augmentation of existing FDS processes.

A rivet rotational feeding method for friction self-piercing riveting (F-SPR) system, comprising: a semi-hollow rivet, a driving spindle and a die. The bottom surface of the rivet head is connected to the semi-hollow rivet shank. The semi-hollow rivet shank has a wedge-shaped end. The rivet head has rotation driving structures and positioning structure on the top end. The rotation driving structures are central symmetric concave or convex surfaces. The positioning structure is a central symmetric and mirror symmetric concave or convex surface. The matching between the driving spindle and the rivet can improve the rotation reliability and positioning accuracy of the riveting at a high rotational speed during F-SPR process, which is beneficial to solve the problems of poor stability and non-coincidence between the geometry axis and the rotation axis of the rivet.

A forging method is provided. The forging comprises determining plans of second and third processes for each of a plurality of ingots, categorizing the plurality of ingots into first and second ingot sets, based on the plans of the second and third processes, evaluating the first and second ingot sets using a scoring function, determining an ingot set to be provided to a first heating furnace, based on the evaluating of the first and second ingot sets, and performing a first process, different from the second and third processes, on the ingot set provided to the first heating furnace.

A forging method is provided. The forging comprises determining plans of second and third processes for each of a plurality of ingots, categorizing the plurality of ingots into first and second ingot sets, based on the plans of the second and third processes, evaluating the first and second ingot sets using a scoring function, determining an ingot set to be provided to a first heating furnace, based on the evaluating of the first and second ingot sets, and performing a first process, different from the second and third processes, on the ingot set provided to the first heating furnace.

A continuously variable transmission includes: a first pulley having a first fixed sheave and a first movable sheave; a first cylinder forming a first oil chamber with the first movable sheave; a second pulley having a second fixed sheave and a second movable sheave; a second cylinder forming a second oil chamber with the second movable sheave; and a transmission belt wound around the first pulley and the second pulley. The first cylinder has a first member that is fixed to a first shaft and a second member that is joined to an outer peripheral portion of the first member. A bearing is interposed between an outer periphery of the first member and an inner periphery of a case. A thickness, in an axial direction, of a portion of the first member that is configured to directly abut against the first movable sheave is larger than a thickness of the second member.

A continuously variable transmission includes: a first pulley having a first fixed sheave and a first movable sheave; a first cylinder forming a first oil chamber with the first movable sheave; a second pulley having a second fixed sheave and a second movable sheave; a second cylinder forming a second oil chamber with the second movable sheave; and a transmission belt wound around the first pulley and the second pulley. The first cylinder has a first member that is fixed to a first shaft and a second member that is joined to an outer peripheral portion of the first member. A bearing is interposed between an outer periphery of the first member and an inner periphery of a case. A thickness, in an axial direction, of a portion of the first member that is configured to directly abut against the first movable sheave is larger than a thickness of the second member.