Texas investor Harold Simmons, rebuffed last April in his attempt to gain control of the board of Lockheed Corp., yesterday offered to buy nation's sixth-largest defense contractor from its shareholders for about $2 billion in cash.

The offer of $40 a share is nearly $10 above what Lockheed stock was trading for yesterday on the New York Stock Exchange.

In making public his offer, Simmons stressed his was not a hostile takeover attempt and sought the cooperation of the California-based maker of the Stealth bomber, the Trident missile, the C-130 Hercules and other defense-related hardware.

But Lockheed's management, which successfully fought off Simmons's bid to gain control of the company at a stockholders meeting last March, replied in a noncommittal manner late yesterday, saying only that it would give the bid "full consideration ... when further details are provided."

Simmons and his NL Industries Inc. already own about 19 percent of Lockheed, having spent $500 million 18 months ago for almost 12 million shares of Lockheed stock.

Since buying the stock, however, Simmons's investment has lost value as the end of the Cold War and the decline of U.S. defense spending drove Lockheed's stock price down -- a drop that Simmons said drove him to try to seize control of the company. He bought his shares at about $40; the stock closed yesterday at $30.25, up 75 cents.

In making the bid yesterday, Simmons aide J. Landis Martin said that Simmons's NL Industries would use $1.3 billion of its own cash and other assets to buy Lockheed, leaving about $800 million more in bank financing that would be required to complete the purchase. "Without the cooperation of Lockheed, that isn't doable in today's capital markets," he added.

In the formal offer sent yesterday to Daniel M. Tellep, Lockheed's chairman and chief executive, Martin openly sought the defense giant's cooperation.

"Dan, I hope you will favorably consider cooperating with NL to give Lockheed shareholders the opportunity to receive $40 per share in cash for their shares," Martin wrote. "In my discussions with major shareholders, there is a strong feeling that absent a transaction such as the one we are proposing, Lockheed stock will not trade near $40 per share for the foreseeable future. Working together, we can deliver this meaningful value to shareholders."

Martin said that he and Simmons tried to arrange a meeting with Tellep over the weekend, but were told the Lockheed chairman was tied up. "I didn't feel rebuffed -- yet," said Martin, who added that he expects to hear from Tellep today.

West Coast industry analysts were somewhat dubious that Lockheed would react favorably to Simmons's $40 per share offer.

"The {$10} premium is not a dramatic one given the fact that Lockheed shares have been undervalued," said Lawrence M. Harris, who follows Lockheed for Bateman Eichler, Hill Richards Inc. in Los Angeles.

Harris suggested that this may be the first shot in a new battle of press releases leading to a new bid for control of Lockheed at the next shareholders meeting in the spring.

Another analyst, Thomas O. Lloyd-Butler of Montgomery Securities in San Francisco, said that an employee-ownership plan that holds 20 percent of Lockheed stock would make it difficult for Simmons to win this battle.

Lockheed had $9.9 billion in sales last year, a 5 percent drop from the year before. But its profits, which were $624 million in 1988, had all but disappeared by last year. In 1989, the company earned $2 million. Profit has improved slightly this year.

The company, which would have gone belly up in 1971 if the federal government had not structured a bailout to save the defense contractor, has most of its operations in California and Georgia, although a few hundred people are employed at an anti-submarine systems center in McLean.

Martin said that the Simmons's group plans no major changes in Lockheed, although he questioned recent attempts to diversify its business by going into computers and aircraft maintenance and repairs. He called these areas "where we don't think they {Lockheed} ought to be."